The invention relates to an active differential for the controlled distribution of a drive torque generated by a drive motor to two output shafts, including a planetary gear train for coupling the output shafts to a drive shaft of the drive motor and a distributor shaft to a distributor motor, wherein the distribution of drive torque to the output shafts depends on a torque exerted by the distributor motor.
Active differentials are used to distribute drive torques to several, in particular two, output shafts. The differential thus allows the two output shafts to have different rotational speeds. When the differential is operated without an additional distributor motor or a complete or partial locking of the differential, the same torques are transmitted to both output shafts. Active intervention in a differential which changes the torque distribution to the output shafts depending on a further introduced torque allows a flexible distribution of torques.
Active differentials are used in particular in motor vehicles for the distribution of the drive torque from a drive motor to the driven wheels of the motor vehicle. In the automotive segment, the use of such an active differential is often referred to as “torque vectoring” or “active yaw”. The use of an active differential in the motor vehicle allows in particular an active influencing of the yaw angle of the motor vehicle, since the torques to the individual wheels and thus the forces being transmitted to the respective wheel on the roadway can be separately controlled or adjusted by the active differential.
In active differentials, even very small differences in speed between the output shafts lead to rotation of the distributor shaft and thus the distributor motor. Since a relatively small-sized motor is typically to be used as a distributor motor, a translation between the rotational speed difference of the drive axles and the distributor shaft is typically provided in order to be able to generate large torque differences between the drive axles with the relatively small-scale distributor motor. Therefore, small differences in rotational speed between drive axles can already lead to a continuous rotation of the distributor motor with a medium rotational speed. This can lead to steady charging and discharging of the battery with low currents, additional mechanical stresses and in particular an uneven load of clocked power electronics. Thus, both the electrical and the mechanical components of the active differential are already stressed at minimum rotational speed differences.
In particular, when an active differential is used in a motor vehicle, however, such strains can occur over long periods, such as when the tires of the motor vehicle are worn unevenly and thus when driving there is always a small difference in rotational speed between the drive axles which are coupled with the tires, or when the weight shift in the motor vehicle is uneven. Even very small steering movements, as they are typically continuously performed by drivers, lead to continual strain on the active differential.